1. Field of the Disclosure
This disclosure relates to a printed circuit board (PCB) and a liquid crystal display (LCD) device with the same, and more particularly to a PCB with superior heat radiation property and to an LCD device including the same.
2. Description of the Related Art
Cathode ray tubes (CRTs), which correspond to one of widely used display devices, are mainly used as monitors for TVs, measuring apparatuses, or information terminals. However, the heavy weight and large size of the CRTs have been a major hindrance to the manufacturing of small, light electronic products.
To address this matter, LCD devices are gradually being used in a wide range of applications due to their advantages such as lightness, thinness, and low power consumption. Accordingly, LCD devices are being manufactured to have even larger screens, be thinner, and consume less power, in order to meet requirements of users. Such LCD devices display images by controlling the amount of light transmitted through liquid crystal.
LCD devices are not self-illuminating display devices, unlike CRTs. As such, an LCD device includes a backlight unit provided on the rear surface of an LCD panel. The backlight unit includes a separated light source providing light necessary to display an image.
The backlight unit can be classified as either an edge type or a direct type in accordance with the disposition of a light source. The edge type backlight unit includes a light source disposed at an inner side surface of it and applies light from the light source to the entire surface of an LCD panel using a light guide plate. On the other hand, the direct type backlight unit includes a plurality of light sources arranged directly under the LCD panel and allows light to be directly applied from the plurality of light sources to the LCD panel.
Recently, the LCD device employs light emission diode (LED) as a light source. Actually, the recent LCD device includes a PCB on which a plurality of LEDs are arranged. The PCB loaded with the plurality of LEDs is used for both the edge and direct type backlight units.
The LED has a serious problem of heat generating phenomenon. This results from the fact that the residual energy not being used in the generation of light is converted into heat. When the heat generated from the LED accumulates into the LCD device without being externally radiated, the LCD device can be deteriorated and decreases its display quality. In addition, if the heat generating phenomenon is continued, durability and reliability of the LED can be deteriorated.
To address this matter, a PCB of the related art is configured to include a copper thin film, a prepreg layer, and a metal layer. In this case, heat generated in LED can be externally radiated through a LED chip, a LED lead frame, the copper thin film of the PCB, the prepreg layer of the PCB, the metal layer of the PCB, and a bottom cover of the LCD device.
However, such a heat radiation path forces heat to pass through many steps. As such, the pregreg layer must function as a critical factor. Therefore, heat radiation characteristic of the LCD device must depend on thermal conductivity of the prepreg layer. More specifically, costs of the LCD device increase as the thermal conductivity of the prepreg layer becomes higher. In view of this point, it is necessary for the PCB and the LCD device to effectively radiate heat generated by the LED toward the exterior.